Reversal of the rotation pattern of a border light system has been achieved in the past by physically reversing a cam clock means that controls the cadence of the light groups. Such mechanisms, operating as they do in a non-uniform manner, tend to be complicated and short lived. Various digital circuits are conceivable for control of solid state switching devices or the like. Yet nothing has proved simpler, more economical and reliable for turning groups of lights on an off than a rotary cam and follower arrangement. The primary object of the present invention is to provide a simple cam clock means of this character that will periodically reverse the rotation or movement pattern of the lights while the cam clock means is driven continuously by a fractional horsepower motor.